10 minute blocks are so much fun and they really are 10 minutes per block. To answer someone's question on puffiness, just be sure that when you sew the final seam, that the fabric is as flat as you can get it (its a little awkward). And if it is puffy, don't worry, you can quilt it out.
I attached a picture of a baby quilt I made using the block. I folded UNDER (not over) the center block sides and hand stitched them down just to neaten the look.